blazer427X3

Well, here I am again writing about this noise I am trying to find and fix.



Here is what I've tried so far ...

Removed main and a/c belts from the car (thats when I shot the video)
Checked compression on all cylinders - good
Inspected all rockers, valve springs and push rods - all okay
Pulled intake, heads and inspected all the lifters - all okay
Inspected cam and checked for movement front/back - all okay
Drained oil and cut open the filter - no shavings found
Oil pressure has always been about 42-45 psi. that hasnt changed
I have never had an overheat issue.
I found a loose plate on the bottom of the intake plenum but even after fixing that the noise is still there.

This noise is like a squealing, scraping sound. It gets faster when I bring the RPM up.

It is the same with the clutch in or out.

When I disconnected the coil packs and cranked the engine as fast at the starter will allow, I do NOT hear the noise.

The car runs, and drives fine ... no vibration, engine miss or anything like that. The noise is really loud and seems to be coming from the rear of the engine.

Could this possibly be a hung starter gear ? Flywheel loose or cracked ? Torque Tube front carrier bearing or bushing ? Has anyone ever heard a noise like this associated with that area ?

All input or suggestions appreciated.

Thanks.

B

lucky131969

You should be able to use a stethoscope to confirm if it's internal or external to the engine.

You done some good work trying to isolate. I edited my comment.........Get a stethoscope.

blazer427X3

Thanks for the reply Lucky

I tried the stethoscope and was not able to isolate it to a particular cylinder. This noise is so loud that I hear it everywhere and its more of a sound like a rotating part scraping on something. When I put my hand down on different areas of the engine while its running I don't feel the noise (if that makes sense). I guess what I am trying to say is that when I have been around an engine with a bad rod or main bearing you can sort of "feel" the knock and this doesn't have any feel.

My good oil pressure and no shavings in the oil and filter also had me thinnking thats not it but at this point I am so baffled by this I am not ruling anything out.

Eric D

Blazer,

Great video and sound capture. It is bad news though. I know that sound very well. My money is on a bad roller on one of the lifters. You can find which one by removing rocker covers and use a stethoscope at each rocker hold-down bolt. The bad one will be heard. Bottomline you will need at least to replace the lifter if this noise just started. If it's been doing it for a while the cam may need to be replace as well.

If you would like to talk in more detail check your PM, I'll leave you my phone number.

blazer427X3

Eric,

Thank you very much for talking with me about this.

I will try the stethoscope on the rocker hold down bolt as the engine runs and post the result. It is very possible that my visual inspection of the lifters wasn't good enough to see the problem. The good thing is that this has not been going on for too long and I parked the car as soon as I could when this occured.

I need to figure this out ... my girlfriend claims I am "preoccupied" and have turned into a grouchy SOB who spends too much time in the garage mumbling to myself. I see my reaction to this problem as perfectly normal of course. I've spent so much time leaning over into the engine compartment that I now have a permanent 45 degree bend in my back.

Once again - Lucky, Eric my thanks for the input !


Blaise

lucky131969

That's a unique noise, and foreign to me...so I'm afraid not much help. Fortunately, Eric has experienced this exact problem/noise...so that helps immensely.

blazer427X3

I agree that Eric knows a lot about the valvetrain on these LS engines and it was a very informative conversation we had. By the way he has some great write ups on lifters and rockers if you go to his profile you can check them out.

I'll be following his suggestion and will post what I find or don't find.

Eric, if this does turn out to be a lifter after all and you want to do a post-mortem on it I will gladly send it to you. I've had that stethoscope stuffed into my ears for so long I am starting to use medical terms for car parts ....



B

Eric D

Nothing to worry about until you start wearing the stethoscope around your neck all the time and anywhere you go. You will start to get some funny looks from folks.....I won't mention how I know that!!

blazer427X3

UPDATE

Noise is loudest on top of #7 intake rocker, can also be heard on #7 exhaust. I can also hear it on the opposite side of the engine on #8 intake and exhaust.

Tearing it down again this weekend, new lifters on the way.

Found a great price on a set of Eaton OEMs. Based on Eric's lifter write up I was able to identify my old ones as Delphi.

Eric D

Blaise,

The cam lobe on #7 intake will really need to be checked over. Because you are hearing it on the other side of the engine make me believe you will be replacing a cam as well. Improper heat treating of the roller or cam lobe can cause this. If you hear it in more than one location most likely means the damage is heavy to the roller and cam lobe surface, just replacing the lifter maybe a short lived fix. Sorry!

blazer427X3

I'll know for sure by the end of the weekend and will share a few pictures of what I find.

I agree that this might have gotten the cam or have been caused by the cam. I have probably run it a total of less than 5 minutes since I had it apart and didn't see anything on the lobes but it will be interesting to see if anything looks different this time.

blazer427X3

Well ... its been an incredibly hectic week and I wasn't able to get to the teardown as expected. My son broke his femur playing Lacrosse and work issues came to the surface so priorities had to be re-adjusted.

So, whats on the menu for this weekend ? LIFTER STEW ! Mmmmm good.



If the cam turns out to be hurt, I can use my Jeg's discount to replace my TSP stick with a CompCams XER 281 HR and hopefully won't need to retune.

TSP 233/239 @50 thou, 595/603 112 LSA (now in the car)

Compcams 232/234 @50 thou, 595/598 112 LSA (poss. replacement)

Eric D

Blaise,

FWIW those are part number 12564012 lifters. The newer replacement number are 12576400. The difference new to old is the newer incase the roller and are 86 grams heavier than the one you have. Preload for the ones you have should be about 1.58mm.

Hope the stew comes out well for you!

blazer427X3

UPDATE

Passenger side head of course comes off sooo easily. Drivers side ? Uuhhh yeah, well that side took a lot more time than I expected. I have to drop the header down because I can't get enough room to get to the bottom row of head bolts, the steering shaft gets in the way and wont allow me to swing the header away from the head far enough. I am taking the day off tomorrow ... its my birthday ... and will finish the teardown. No metal inside the oil filter (second one I've cut open).

I did notice that the spark plug on #5 cylinder is sooty black. All the others are light tan as they should be.

Pictures and hopefully a full damage report tomorrow night !

Thanks again Eric and Lucky, the opportunity to vent and think out loud in writing along with your input and suggestions have been really helpful.

Blaise

Eric D

Blaise,

Hey hope you have a Happy Birthday!

blazer427X3

Thanks Eric. It will be a REALLY happy one if I didn't wipe a lobe !

Whatever it turns out to be I will know for sure tomorrow I guess. I just miss driving the car and want to fix it.



B

daleweible

Happy Birthday!

blazer427X3

Thanks Dale !

I got a great present today too, my cam is fine, no damage !!!

daleweible

Good news all the way around, I'm lucky was a good shade tree but one of my old friends is a gear head, worked in Buick engineering for years and has an 2000 with about 500 rwhp. I'm kind of patrial to stock with maybe a little something extra. I just got the $1000 pot hole upm here in Michigan.

blazer427X3

Eric,

I'll post a picture of the failed lifter, #5 intake, later this evening and I'll send it to you if you want to do an autopsy. It looks like it was beginning to fracture at the edges of the roller where the flat part meets the beveled edge on the side. The marks are very small, about the size of a ballpoint pen tip. The damage is very subtle, but its there and I am glad I found it. I think the spark plug being darker on that cylinder compared to the others is from a crispy plug wire that was too close to the header. Just a coincidence that it was on the same cylinder as the bad lifter. I also found a massive intake leak near that cylinder on the first teardown. The cam looks fine I checked every bit of each lobe, no scarring, unusual wear on any of them. I looked #5 over VERY closely and cant see any damage.



B